The range measures the whole spread; the interquartile range measures the spread of the middle half, where most of the data sits. These free printable worksheets give seven numbers and ask for the IQR — worked so every quartile is a whole number.
If they get stuck
The answer key prints on a separate page.
The method is order, split, subtract. Put the seven numbers in order, cross out the one in the middle to leave a lower half and an upper half, and the middle of each half is a quartile: Q1 below, Q3 above. The interquartile range is Q3 minus Q1. Saying it as "the middle of the bottom, the middle of the top, the gap between them" is what keeps it from blurring into the plain range.
Seven numbers is deliberate, not arbitrary. With an odd half on each side, Q1 and Q3 land on actual data values rather than halfway between two — so the quartiles and the IQR are whole numbers, and a sixth-grader is never asked to write 12.5 in a blank meant for a whole. It is the same reason the mean sheets build their totals to divide evenly.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Interquartile range, step by step